This invention relates, in general, to multi-ply soft tissue paper products; and more specifically, to multi-ply soft tissue paper products having a multi-region paper structure with a surface-applied chemical softeners applied to at least one of the regions.
Sanitary paper tissue products are widely used. Such items are commercially offered in formats tailored for a variety of uses such as facial tissues, toilet tissues and absorbent towels.
All of these sanitary products share a common need, specifically to be soft to the touch. Softness is a complex tactile impression evoked by a product when it is stroked against the skin. The purpose of being soft is so that these products can be used to cleanse the skin without being irritating. Effectively cleansing the skin is a persistent personal hygiene problem for many people. Objectionable discharges of urine, menses, and fecal matter from the perineal area or otorhinolaryngogical mucus discharges do not always occur at a time convenient for one to perform a thorough cleansing, as with soap and copious amounts of water for example. As a substitute for thorough cleansing, a wide variety of tissue and toweling products are offered to aid in the task of removing from the skin and retaining such discharges for disposal in a sanitary fashion. Not surprisingly, the use of these products does not approach the level of cleanliness that can be achieved by the more thorough cleansing methods, and producers of tissue and toweling products are constantly striving to make their products compete more favorably with thorough cleansing methods.
Shortcomings in tissue products for example cause many to stop cleaning before the skin is completely cleansed. Such behavior is prompted by the harshness of the tissue, as continued rubbing with a harsh product can abrade the sensitive skin and cause severe pain. The alternative, leaving the skin partially cleansed, is chosen even though this often causes malodors to emanate and can cause staining of undergarments, and over time can cause skin irritations as well. Disorders of the anus, for example hemorrhoids, render the perianal area extremely sensitive and cause those who suffer such disorders to be particularly frustrated by the need to clean their anus without prompting irritation.
Accordingly, making soft tissue and toweling products has long been the goal of the engineers and scientists who are devoted to research into improving tissue paper. While softness is the paramount attribute affecting the desirability and effectiveness of a tissue paper product, it""s achievement has often been pursued even at the expense of making performance impairing sacrifices.
For example, it is well known that there is an inverse relationship between softness of tissue paper products and the strength of those products. Strength is the ability of the product, and its constituent webs, to maintain physical integrity and to resist tearing, bursting, and shredding under use conditions. Tissue paper webs are normally moderated in strength to the minimum level required in order to maximize the potential for softness.
Another area which has been long been sacrificed to maximize softness is texture. A tissue paper web is typically sided due to the processes used to produce paper products. Sidedness is the tendency for one side of the paper web to be smoother than the other side. For example, in a so-called Yankee-type or dry creped process, there is substantial smoothing achieved by contact of one side of the sheet with the Yankee. Analogously, in an uncreped process, the different drying fabrics with which the sides of the web are in contact during production have different smoothness characteristics; these differences are replicated in the surfaces of the resultant product. The resultant smooth versus. textured side of tissue paper webs present the manufacturer of tissue paper products with a dilemma when the tissue paper webs are used to assemble a multi-ply product. For example, in common two-ply tissue product, it is typical practice to orient the smoother side of the individual tissue paper webs toward the outward facing surfaces. This orientation is selected to maximize softness by maximizing the smoothness of the tissue paper product. Smoothness is one characteristic used by consumers to determine relative softness and is a tactilely perceivable difference in texture (lowering texture increases smoothness) resulting from the intrinsic nature of the tissue papermaking process. Those skilled in the art will recognize that the perceived softness improvement from orienting the smoother side out is accompanied by a sacrifice in the cleaning potential (or perceived cleaning potential) of the product that would be provided by the rougher texture (An example of the recognition by the art of the value of texture to cleaning can be found in U.S. Pat. No. 4,112,167, issued to Dake, et al. on Sep. 5, 1978, which describes tissue structures having surface depressions, the structure being treated with a lipophilic cleansing emollient at a level of between about 10 percent and about 150 percent of the tissue weight). Notwithstanding the sacrifice in cleaning potential, the art has consistently chosen to convert multi-ply products smooth side out because of the softness deficiencies of products converted with the rougher side out. Thus, it would be highly desirable to convert the tissue paper webs into multi-ply products so that textured surfaces face outward, if softness could be maintained.
Various methods have been undertaken to increase softness of tissue paper webs. For, example, one area that has been exploited in this regard has been to select and modify cellulose fiber morphologies and engineer paper structures to take optimum advantages of the various available morphologies. Applicable art in this area includes: Vinson et. al. in U.S. Pat. No. 5,228,954, issued Jul. 20, 1993, Vinson in U.S. Pat. No. 5,405,499, issued Apr. 11, 1995, Cochrane et al. in U.S. Pat. No. 4,874,465 issued Oct. 17, 1989, and Hermans, et. al. in U.S. Statutory Invention Registration H 1672, published on Aug. 5, 1997, all of which disclose methods for selecting or upgrading fiber sources to tissue and toweling of superior properties. Applicable art is further illustrated by Carstens in U.S. Pat. No. 4,300,981, issued Nov. 17, 1981, which discusses how fibers can be incorporated to be compliant to paper structures so that they have maximum softness potential. While such techniques as illustrated by these prior art examples are recognized broadly, they can only offer some limited potential to make tissues truly effective comfortable cleaning products.
Another area which has received a considerable amount of attention is the addition of chemical softening agents (also referred to herein as xe2x80x9cchemical softenersxe2x80x9d) to tissue and toweling products.
As used herein, the term xe2x80x9cchemical softening agentxe2x80x9d refers to any chemical ingredient which improves the tactile sensation perceived by the consumer who holds a particular paper product and rubs it across the skin. Although somewhat desirable for towel products, softness is a particularly important property for facial and toilet tissues. Such tactile perceivable softness can be characterized by, but is not limited to, friction, flexibility, and smoothness, as well as subjective descriptors, such as a feeling like lubricious, velvet, silk or flannel. which imparts a lubricious feel to tissue. This includes, for exemplary purposes only, basic waxes such as paraffin and beeswax and oils such as mineral oil and silicone oil as well as petrolatum and more complex lubricants and emollients such as quaternary ammonium compounds with long alkyl chains, functional silicones, fatty acids, fatty alcohols and fatty esters.
The field of work in the prior art pertaining to chemical softeners has taken two paths. The first path is characterized by the addition of softeners to the tissue paper web during its formation either by adding an attractive ingredient to the vats of pulp which will ultimately be formed into a tissue paper web, to the pulp slurry as it approaches a paper making machine, or to the wet web as it resides on a Fourdrinier cloth or dryer cloth on a paper making machine.
The second path is categorized by the addition of chemical softeners to tissue paper web after the web is dried. Applicable processes can be incorporated into the paper making operation as, for example, by spraying onto the dry web before it is wound into a roll of paper.
Exemplary art related to the former path categorized by adding chemical softeners to the tissue paper prior to its assembly into a web includes U S. Pat. No. 5,264,082, issued to Phan and Trokhan on Nov. 23, 1993, incorporated herein by reference. Such methods have found broad use in the industry especially when it is desired to reduce the strength which would otherwise be present in the paper and when the papermaking process, particularly the creping operation, is robust enough to tolerate incorporation of the bond inhibiting agents. However, there are problems associated with these methods, well known to those skilled in the art. First, the location of the chemical softener is not controlled; it is spread as broadly through the paper structure as the fiber furnish to which it is applied. In addition, there is a loss of paper strength accompanying use of these additives. While not being bound by theory, it is widely believed that the additives tend to inhibit the formation of fiber to fiber hydrogen bonds. There also can be a loss of control of the sheet as it is creped from the Yankee dryer. Again, a widely believed theory is that the additives interfere with the coating on the Yankee dryer so that the bond between the wet web and the dryer is weakened. Prior art such as U.S. Pat. No. 5,487,813, issued to Vinson, et. al., Jan. 30, 1996, incorporated herein by reference, discloses a chemical combination to mitigate the before mentioned effects on strength and adhesion to the creping cylinder; however, these methods continue to be inadequate to provide for a cleaning product which is at the same time textured on its surface and soft.
Further exemplary art related to the addition of chemical softeners to the tissue paper web during its formation includes U.S. Pat. No. 5,059,282, issued to Ampulski, et. al. on Oct. 22, 1991 incorporated herein by reference. The Ampulski patent discloses a process for adding a polysiloxane compound to a wet tissue web (preferably at a fiber consistency between about 20% and about 35%). Such a method represents an advance in some respects over the addition of chemicals into the slurry vats supplying the papermaking machine. For example, such means target the application to one of the web surfaces as opposed to distributing the additive onto all of the fibers of the furnish. However, such methods fail to overcome the primary disadvantages of the addition of chemical softeners to the wet end of the papermaking machine, namely the strength effects and the effects on the coating of the Yankee dryer, should such a dryer be employed.
Because of the before mentioned effects on strength and disruption of the papermaking process, considerable art has been devised to apply chemical softeners to already-dried paper webs either at the so-called dry end of the papermaking machine or in a separate converting operation subsequent to the papermaking step. Exemplary art from this field includes U.S. Pat. No. 5,215,626, issued to Ampulski, et. al. on Jun. 1, 1993; U.S. Pat. No. 5,246,545, issued to Ampulski, et. al. on Sep. 21, 1993; U.S. Pat. No. 5,525,345, issued to Warner, et. al. on Jun. 11, 1996, and U.S. patent application Ser. No. 09/053,319 filed in the name of Vinson, et al. on Apr. 1, 1998 all incorporated herein by reference. The U.S. Pat. No. 5,215,626 discloses a method for preparing soft tissue paper by applying a polysiloxane to a dry web. The U.S. Pat. No. 5,246,545 discloses a similar method utilizing a heated transfer surface. The Warner Patent discloses methods of application including roll coating and extrusion for applying particular compositions to the surface of a dry tissue web. Finally, the Vinson, et al. application discloses compositions that are particularly suitable for surface application onto a tissue web. While each of these references represent advances over the previous so-called wet end methods particularly with regard to eliminating the degrading effects on the papermaking process, none are effective at providing for an product which is strong, textured on its outer surfaces and soft.
Accordingly, there is a continuing need for soft, multi-ply tissue paper products in which one or more of the constituent plies is orientated with a textured surface on an outer face.
Such products are provided by the present invention as is shown in the following disclosure.
The present invention is a multi-ply soft tissue paper product. At least one of the plies of this product has an inner face and an outer face, wherein the inner face is defined as the face directed toward the interior of the product and therefore not exposed while the outer face is directed toward the exterior of the product and is exposed to the touch of a user. The outer face, by virtue of the converting process applied to a substrate made using a multi-region papermaking process, comprises multiple regions wherein there is a first region that is raised above a second region. At least the first region has a surface deposited chemical softening composition disposed on at least a portion thereof.
The first region comprises raised portions that are provided at a frequency suitable to provide the desired texture. Suitably, the texture frequency of the first region is less than 50/in (20/cm). Preferably, the texture frequency of the first region is less than 30/in (12/cm). More preferably, the texture frequency of the first region is less than 20/in (8/cm). Further, the texture frequency is at least about 2/in (0.8/cm), preferably more than about 4/in (1.6/cm), and more preferably more than about 6/in (2.4/cm). The term xe2x80x9ctexture frequencyxe2x80x9d as used herein refers to the number of times that the raised portions comprising the first region of the outer face of the tissue ply repeat over a given distance. Typically, the raised portions repeat in a regular pattern, but irregular repeating patterns are also anticipated. It is also anticipated that the observed frequency will vary depending on the direction relative, for example, to the machine direction of the tissue paper ply. As used herein, the frequency is defined as measured in the direction which yields the highest frequency measurement as defined above.
The present invention also comprises softening compositions that, when applied to the above-described tissue webs, preferably dried tissue webs, provide soft, strong, absorbent, and aesthetically pleasing tissue paper. The composition is a dispersion comprising:
an effective amount of a softening active ingredient;
a vehicle in which the softening active ingredient is dispersed;
an electrolyte dissolved in the vehicle, the electrolyte causing the viscosity of the composition to be less than the viscosity of a dispersion of the softening composition in the vehicle alone; and
a nonionic surfactant to further reduce the viscosity of the softening composition.
The term xe2x80x9cvehiclexe2x80x9d as used herein means a fluid that completely dissolves a chemical papermaking additive, or a fluid that is used to emulsify a chemical papermaking additive, or a fluid that is used to suspend a chemical papermaking additive. The vehicle may also serve as a carrier that contains a chemical additive or aids in the delivery of a chemical papermaking additive. All references are meant to be interchangeable and not limiting. The dispersion is the fluid containing the chemical papermaking additive. The term xe2x80x9cdispersionxe2x80x9d as used herein includes true solutions, suspensions, and emulsions. For purposes for this invention, all terms are interchangeable and not limiting. If the vehicle is water or an aqueous solution, then, preferably, the hot web is dried to a moisture level below its equilibrium moisture content (at standard conditions) before being contacted with the composition. However, this process is also applicable to tissue paper at or near its equilibrium moisture content as well.
The amount of papermaking additive applied to the tissue paper is, preferably, between about 0.1% and about 8% based on the total weight of the softening composition compared to the total weight of the resulting tissue paper. The resulting tissue paper preferably has a basis weight of from about 10 to about 80 g/m2 and a fiber density of less than about 0.6 g/cc.
All percentages, ratios and proportions herein are by weight, unless otherwise specified.